A  diet  high  in  cocoa  bean  flavanols—naturally  created  dietary  compounds  found  within  the  cocoa bean—may enhance cognitive function in older individuals, according to a new study from Columbia University, New York.

Age-related cognitive decline is associated with changes in a brain region called the dentate gyrus (DG).  Previous studies report that age-related decreases in function of the DG may be involved in memory decline over time.

Study method

The study, published online recently in Nature Neuroscience, found that study participants who consumed a high dose of cocoa flavanols over three months performed a delayed-recognition memory task much faster than those who received a low flavanol dose.

Scott  A.  Small  and  colleagues  examined  whether  cocoa  flavanols,  would  enhance  DG function and cognitive performance in 37 older participants, aged 50-69, who were given either a high or a low dose of  cocoa flavanols for three months.

From brain scans obtained, both before and after three months of flavanol consumption, the researchers found that this flavanol-improved performance was  correlated  with  increased  cerebral  blood  volume  in  the  DG,  suggesting  that  high  consumption of  dietary  cocoa  flavanols  can  enhance  DG  function,  and  therefore  cognitive  function,  in  older individuals.

‘Exciting’ findings, experts

Dr Ashok Jansari, Cognitive Neuropsychologist, Department of Psychology, Goldsmiths College (University of London), said the study was ‘exciting’ because it isolated a part of the ‘memory centre’ of the brain known as the hippocampus and a particular section within it called the dentate gyrus.

“This area is important because while there is a general weakening of hippocampal functioning with age, the dentate gyrus is seen to be particularly involved in this healthy age-related decline,” Dr Jansari said. “Crucially, this area is different to another area within the hippocampus, the ‘entorhinal cortex’ which seems to be affected in Alzheimer’s Disease and therefore the functional integrity of the dentate gyrus is of special interest given that globally, there is a growing ageing population and the majority of these are neurologically healthy and are not affected by Alzheimer’s,” he said.

“By refining very complex neuroimaging techniques that allow changes in biological activity to be measured, the authors were able to examine how functioning of the gyrus is affected by certain chemicals found in cocoa called flavanols,” Dr Jansari said.

Dr Jansari said the study had a few limitations, largely to do with the size of the sample.

“However, given the complexity of the design of the study and its longitudinal nature requiring follow-up over three months, the findings simply suggest that larger scale and longer-term follow-ups are required,” Dr Jansari said. “Given a globally ageing population, by isolating a particular area of the brain that is weakening in functioning as we grow older, and demonstrating that a non-pharmacological intervention can improve learning of new information, the authors have made a significant contribution to helping us improve our cognitive health,” he said.

Dr Liz Coulthard, Consultant Senior Lecturer in Dementia Neurology, University of Bristol, said the study hinted at a reversal of age-related memory loss through dietary modification which was an appealing prospect for an ageing population, “particularly when the dietary supplement is cocoa-based”.

Dr Coulthard also highlighted the small scale of the study as a limitation, as well as small differences in caffeine and theobromine levels in the high and low flavanol cocoa sachets, which she said made it “possible that substances other than flavanols mediated the effects”. Dr Coulthard said that the study also found that only reaction times, and not accuracy of performance, were actually improved and that “being faster without being more accurate is not always an advantage”.

“It would be very exciting if such a cognitive benefit of flavanols were shown in a larger study that probed several aspects of cognition,” Dr Coulthard said.

The paper can be found here.

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